Trusted operating systems (OS) and platforms are a relatively new concept. In first generation platforms, a trusted (trusted) environment is created where applications can run trustedly and tamper-free. The security is created through changes in the processor, chipset, and software to create an environment that cannot be seen by other applications (memory regions are protected) and cannot be tampered with (code execution flow cannot be altered). Second generation trusted platforms may add trusted graphics and input/output units. Trusted graphics would allow for the OS to display messages to the end user that cannot be tampered with, and trusted I/O would allow for keystrokes and mouse movements to be entered in a trusted fashion.
In desktop platforms, trusted keystrokes will be entered on an external keyboard. In an environment supporting trusted I/O, the keyboard will need to be certified as a trusted input device, and the hardware and firmware design will need to be certified by one or more third party agencies.
In mobile platforms, an embedded controller, commonly referred to as the keyboard controller, currently supports the integrated keyboard. The keyboard controller is responsible for scanning the matrix keyboard by periodically driving a series of general-purpose output lines in a sequential fashion to the keyboard matrix. By then reading back another series of general-purpose input lines, the keyboard controller can detect keystrokes. Unfortunately, these keystrokes today are sent to the system through the legacy keyboard interface. It is expected that this interface will not be deemed trusted in a trusted environment.
In addition to this, there are many issues, which may prevent mobile embedded controllers from being deemed trusted. These devices contain large amounts of OEM-specific code in the embedded controller to perform duties such as thermal management, power plane control, docking interfaces, ACPI interfacing, all of which is unrelated to keyboard control. The presence of all this unrelated code may not meet the requirements of a trusted I/O device.